The present invention is directed to a process for the preparation of optically active (C.sub.1 -C.sub.3)alkyl 2R-chroman-2-carboxylates via the partial enzymatic hydrolysis of the corresponding racemic ester using a microbial lipase derived from Pseudomonas fluoroescens. The present invention is further directed to intermediates and a multistep process for converting said 2R-chroman-2-carboxylate to 2R-benzylchroman-6-carbaldehyde, a known compound of known utility as an intermediate in the manufacture of the known hypoglycemic agent of the formula ##STR1## (See Eggler et al., U.S. Pat. No. 4,703,052 for details).
Optically active chroman-2-carboxylic acids and corresponding alkyl esters are generally known compounds; for example, see Schaaf et al., J. Med. Chem., v. 26, pp. 328-334 (1983). Lipase mediated resolution of some structurally related hydroxylated chroman-2-carboxylates have been recently reported in published European patent application no. 325,954.
The chemical nomenclature used herein is generally that of Rigaudy et al., IUPAC Nomenclature of Organic Chemistry, 1979 Edition, Pergammon Press, New York. An alternative name for chroman, ##STR2## is (2H)-3,4-dihydro-1-benzopyran. An alternative name for chromene, ##STR3## is (4H)-1-benzopyran.